Devices and methods for sensing condensation conditions and for preventing and removing condensation from surfaces

ABSTRACT

A device and method is provided for sensing or predicting when condensation having a given physical state is present or imminent and for suppressing such condensation from a surface, such as a vehicle windscreen, eyewear, goggles, helmet visor, computer monitor screen, window, electronic equipment, etc, by preventing or removing it. A first thermal sensor is in thermally conductive contact with the surface. A second thermal sensor is in an environment separated from the surface. A humidity sensor is in the environment of the second thermal sensor. A circuit causes a condensation suppression mechanism to be activated for preventing or removing condensation having the given physical state from the surface when a temperature sensed by the first thermal sensor, a temperature sensed by the second thermal sensor, and a humidity sensed by the humidity sensor indicate that a condensation condition is either present or imminent and requires prevention or removal at the surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of Patent Cooperation Treatyapplication PCT/US02/29422, filed Sep. 18, 2002, the entire disclosureof which is hereby incorporated herein by reference, which is acontinuation of U.S. application Ser. No. 09/953,891, filed on Sep. 18,2001, now U.S. Pat. No. 6,470,696, the entire disclosure of which ishereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to devices and methods for sensingcondensation conditions and for preventing or removing such condensationfrom surfaces such as vehicle windscreens, eyewear, goggles, helmetvisors, computer monitor screen, windows, electronic equipment, etc.,and especially devices and methods that use a thermal sensor and ahumidity sensor in an adjacent ambient space with respect to thesurface, or in thermally conductive contact with a thermoelectric cooler(TEC), for automatically and dynamically sensing condensation conditionswhen condensation appears on a surface or before such condensationactually appears on a surface.

BACKGROUND

The level of moisture in air at any time is commonly referred to asrelative humidity. Percent relative humidity is the ratio of the actualpartial pressure of steam in the air to the saturation pressure of steamat the same temperature. If the actual partial pressure of steam in theair equals the saturation pressure at any given temperature, therelative humidity is 100 percent. If the actual partial pressure is halfthat of the saturation pressure, the relative humidity is 50 percent,and so forth.

Dew point temperature, also known as condensation temperature orsaturation temperature, is a function of the level of moisture or steamthat is present in the air, and is the temperature at which air has arelative humidity of 100 percent. Condensation of moisture on a surfaceoccurs when the temperature of that surface is at or below the dew pointtemperature of air surrounding the surface.

When air having a relatively high content of moisture comes into contactwith a surface having a temperature at or below the dew pointtemperature, steam will begin to condense out of the air and deposit aswater droplets onto the surface. At this time, a thin layer of liquidwater comprised of small water droplets forms on the surface, creating avisual hindrance or “fog” to an observer looking at or through thesurface. Once, formed, the condensation can be dispersed and removedeither by raising the temperature of the surface, thereby changing thewater into steam, or by lowering the relative humidity of the airsurrounding the surface, thereby allowing the droplets to evaporate.

Steam, as a gas, exists in a saturated state at pressures andcorresponding temperatures that are predictable and measurable. Notably,the standard for steam's thermodynamic properties, including saturationpressures and temperatures, in the United States and arguably the world,is the ASME (American Society of Mechanical Engineers) Steam Tables.These thermodynamic property tables are readily obtainable from ASME, aswell as from engineering texts.

In that steam possesses certain characteristics and traits as asaturated gas that are measurable and exact, equations have beendeveloped that permit the engineer to approximate and predict theproperties of steam at a desired set of conditions when its propertiesare known at a different, or datum, set of conditions. Such an equation,in the case of gas saturation pressures and temperatures, is entitledthe Clausius-Clapeyron Equation. This equation, which may be describedin several variations, may be best stated for the purposes at hand inthe following form:${\ln \quad\left\lbrack \frac{P_{2}^{\quad {sat}}}{P_{1}^{\quad {sat}}} \right\rbrack} = {\frac{\Delta \quad H}{R}*\left( {\frac{1}{T_{1}} - \frac{1}{T_{2}}} \right)}$

where

P₁ ^(sat) is the saturation partial pressure at state 1, in units ofpsia;

P₂ ^(sat) is the saturation partial pressure at state 2, in units ofpsia;

ΔH is the heat of vaporization, equal to approximately 755,087.46(ft−lbf)/lbm for steam;

R is the gas constant, equal to approximately 85.8 (ft−lbf)/(lbm−° R)for steam;

T₁ is the temperature at state 1, in units of degrees Rankine; and

T₂ is the temperature at state 2, in units of degrees Rankine.

Thus, using the Clausius-Clapeyron Equation, once steam 's saturationpressure and temperature are known (the saturation pressure andtemperature defining state 1 of the steam), given any other desiredtemperature, the saturation pressure at this temperature can becalculated to a high degree of accuracy (the temperature and calculatedsaturation pressure defining state 2 of the steam). Conversely, givenany known state 1 conditions, for any desired saturated gas pressure,the saturation temperature can be calculated (the saturation pressureand calculated temperature defining state 2 of the steam).

SUMMARY

The invention provides a device and method for sensing or predictingwhen condensation is present or imminent and for suppressing suchcondensation from a surface by preventing it or removing it. A firstthermal sensor is in thermally conductive contact with the surface. Asecond thermal sensor is in an environment separated from the surface. Ahumidity sensor is in the environment of the second thermal sensor. Acircuit causes a condensation suppression mechanism to be activated forpreventing or removing condensation having the given physical state fromthe surface when a temperature sensed by the first thermal sensor, atemperature sensed by the second thermal sensor, and a humidity sensedby the humidity sensor indicate that a condensation condition is eitherpresent or likely and requires prevention or removal at the surface. Asused herein and in the claims, the term “suppress” encompassesprevention or preclusion of condensation conditions as well as, in thealternative, removal of existing condensation conditions.

The invention provides a convenient and practical mechanism fordetecting condensation conditions quickly, before they manifestthemselves on the surface. In certain embodiments the condensationsuppression mechanism can be activated automatically when a condensationcondition is detected, thereby providing convenience and safety wherethe surface is a windscreen of a vehicle, for example, or goggles, ahelmet visor, computer monitor screen, window, electronic equipmentenclosure.

In one embodiment of the invention, the second thermal sensor is inthermally conductive contact with a cooling device, and a circuitactivates the cooling device in order to maintain the second thermalsensor at a temperature that is lower than a temperature of the firstthermal sensor. The humidity sensor is in thermally conductive contactwith the cooling device. The circuit causes the condensation suppressionmechanism to be activated when the humidity sensor indicates a presenceof high humidity conditions or condensation at the temperature that islower than the temperature of the first thermal sensor.

In alternative embodiments of the invention, the environment of thesecond thermal sensor is in an adjacent ambient space with respect tothe surface. The circuit determines that the condensation conditionrequires suppression at the surface by determining, from the temperaturesensed by the second thermal sensor and the humidity sensed by thehumidity sensor, the pressure of steam in the environment of the secondthermal sensor. Then, the circuit may either determine a ratio of thepressure of steam in the environment of the second thermal sensor to thesaturated steam pressure at the temperature sensed by the first thermalsensor, or determine a difference between a temperature sensed by thefirst thermal sensor and a dew point temperature associated with thepressure of steam in the environment of the second thermal sensor.

Thus, in certain embodiments of the invention, instead of measuring RHat an intentionally lowered temperature relative to the surface inquestion, RH (and temperature) can be measured in the surroundingambient air adjacent to and in the proximity of the surface itself.Through calculation, the measurements taken in the surrounding ambientair can be extrapolated using the Clausius-Clapeyron Equation or any ofits derivatives to determine whether condensation conditions exist onthe surface in question or are imminent. Thus, it is not necessaryphysically to create a simulated (state 2) temperature in which a (state2) relative humidity (RH) value can be measured.

Numerous additional features, objects, and advantages of the inventionwill become apparent from the following detailed description, drawings,and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a surface in combination with a pair of thermalsensors in accordance with the invention.

FIG. 2 is a cross-sectional drawing of two options for incorporating athermal sensor into a surface.

FIG. 3 is a cross-sectional drawing of thermoelectric cooler accordingto the invention in combination with a thermal sensor.

FIG. 4 is a block diagram of the electrical circuitry for an automaticsensing system according to the invention.

FIG. 5 is a block diagram of the electrical circuitry for two options ofa condensation suppression system configured to be combined with theautomatic sensing system of FIG. 4.

FIG. 6 is a drawing of the thermoelectric cooler and thermal sensor ofFIG. 3 within an air duct, the air duct being shown in partial cut-awayview.

FIG. 7 is a flow diagram of a method for automatically sensingcondensation conditions and for suppressing condensation from surfacesusing the system illustrated in FIGS. 1-6.

FIG. 8 is a diagram of a surface in combination with a pair of thermalsensors and a humidity sensor in accordance with another embodiment ofthe invention

FIG. 9 is a cross-sectional drawing of two options for incorporating athermal sensor into a surface.

FIG. 10 is a block diagram of electrical circuitry for automatic sensingsystems according to the invention of the type shown in FIG. 8.

FIG. 11 is a block diagram of the electrical circuitry for threeembodiments of a condensation suppression system configured to becombined with the automatic sensing system of FIG. 10.

FIG. 12 is a drawing of a condensation detection and suppression system,in accordance the invention, applied to a pair of goggles.

FIG. 13 is an exploded view of a portion of the electronic circuitrysensors juxtaposed relative to their protective hydrophobic cover asembodied in FIG. 12.

FIG. 14 is a flow diagram of a method for automatically sensingcondensation conditions and for suppressing such conditions from asurface using the system illustrated in FIGS. 10 and 11.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

With reference to FIG. 1, an automatic sensing and condensationprevention and removal system according to the invention includes twothermal sensors 2 and 6. Thermal sensor 2 is mechanically affixed to orembedded within a surface 1 from which condensation conditions are to besensed and/or condensation is to be removed, such as a windscreen,goggles, a visor for a military helmet, pilot helmet, space-suit helmet,or other type of helmet, a computer monitor screen (such as a screen fora commercial electron beam or LCD computer monitor placed outdoors or ina high-humidity environment, such as in an industrial panel), a windowor other transparent or translucent pane or enclosure (such as commonwindows in office buildings or enclosures that may house documents orother sensitive materials such as artwork and artifacts in museums orhistoric works), including plastics, an electronic equipment enclosure(such as a transparent or non-transparent enclosure for computerequipment, telecommunications equipment, etc. that might be placedoutdoors or in high-humidity environments in which condensation mightappear on the inside surface of the enclosure).

Each of the thermal sensors is a thermocouple formed by the thermalfusion of two dissimilar but electrically insulated metal conductors. Inparticular, the thermal fusion of metal conductors 3 and 4 forms thermalsensor 2 and the thermal fusion of metal conductors 3 and 7 formsthermal sensor 6. Conductors 4 and 7 are of the same electro-conductivematerial and are of the same length.

If the temperatures of the bodies sensed by thermal sensors 2 and 6 areexactly the same, the thermocouple circuit through conductors 4 and 7creates no electrical current. If the temperatures are not identical, acurrent is generated through this thermocouple circuit throughconductors 4 and 7, this current being proportional to the temperaturedifference of the two thermocouple junctions, as was first discovered byThomas Seebeck in 1821.

The integrated sensing and condensation prevention and removal devicecreates an intentional temperature difference between thermocouples 2and 6 by the thermoelectric cooling effect of a thermoelectric cooler(TEC) onto which thermocouple 6 is mechanically affixed.

With reference to FIG. 2, thermal sensor 2 may be mechanically affixedto surface 1 by an adhesive 5 (Option 1), or thermal sensor 2 may beembedded within surface 1 (Option 2).

With reference to FIG. 3, thermal sensor 6 is mechanically affixed bymeans of an adhesive 17 to the exterior face of the cold junction side 9of thermoelectric cooler (TEC) 8. The exterior face of the hot side 10of TEC 8 may be mechanically bonded or otherwise attached to an optionalheat sink 12. A humidity sensor 13, illustrated as a thin-filmcapacitive sensor but which may be any other sensing device thatperforms a similar function, is bonded by a mechanical bond 18 tothermocouple 6. Thus, TEC cold-side face 9, thermocouple 6, andcapacitive sensor 13 will always be at the same temperature. Withreference to FIG. 6, TEC 8, thermal sensor 6, and thin-film capacitivesensor 13 are placed within the recirculation or outside air duct 58,with heat sink 12 being attached to air duct 58.

With reference to FIG. 4, as the above-mentioned intentionally-createdtemperature difference is created between thermocouples 2 and 6, and,consequentially, as current is developed within the thermocouplecircuit, the resultant voltage difference across conductors 4 and 7 ismeasured and amplified by voltage amplifier circuit 19. This voltagesignal is adjusted and offset for any impressed thermocouple effects dueto any dissimilar metal junctions created by the connection ofconductors 4 and 7 to voltage amplifier circuit 19 itself. The voltagesignal is thereafter fed to TEC controller circuit 20, within which thesignal is compared to a pre-established differential voltage set point.Thereafter, TEC controller circuit 20, supplied with an electrical powersource and electrically grounded at ground 28, electrically modulates avoltage that is applied to TEC 8 by conductors 14 and 15, in order tomaintain the cold face of TEC 8 at a temperature level that is apredetermined amount below the temperature of the windscreen, goggles,helmet visor, computer monitor screen, window, electronic equipmentenclosure, or other surface.

The integrated sensing and condensation prevention and removal device isoperated in a manner such that a constant difference is dynamicallymaintained between the temperature established at thermal sensor 6 bythe action of TEC 8 and the temperature measured at the surface bythermal sensor 2. Therefore, regardless of the temperature of thesurface, the temperature established at the cold-side face of TEC 8 ontowhich thermal sensor 6 is affixed will always be lower than that of thesurface by a predetermined amount.

Ambient air or outside air flows over thin-film capacitive sensor 13.The capacitance of capacitive sensor 13 will be proportional to therelative humidity of the surrounding air. Because capacitive sensor 13is maintained at a temperature less than that of the windscreen,goggles, helmet visor, computer monitor screen, window, electronicequipment enclosure, or other surface, the humidity level sensed willalways be greater than that at the surface, and any liquid condensationwill always form on capacitive sensor 13 before it forms on the surface.

Thin-film capacitive sensor 13 is connected by conductors 22 and 23 tocapacitance-to-voltage circuit 29. Conductor 23 andcapacitance-to-voltage circuit 29 are connected to a common electricalground 40. Capacitance-to-voltage circuit 29 is supplied regulated2.5-volt DC power by conductor 27 from voltage regulator circuit 26,which is in turn energized by an electrical power source and anelectrical ground 28. Capacitance-to-voltage circuit 29 includes two#7556 timing integrated circuits 30 and 33, resistors 34, 35, 37, and39, and filter capacitors 31, 38, and 41. Timing integrated circuits 30and 33 are electrically grounded at junctions 32, 36, 42, and 44.

Capacitance-to-voltage circuit 29 transforms the constant 2.5-volt DCsupply voltage into a high-frequency AC signal. Thin-film capacitivesensor 13 is integrated into capacitance-to-voltage circuit 29 in amanner such that any capacitance of capacitive sensor 13 is transformedinto a positive DC voltage relative to ground 44, at conductor 43 ofcapacitance-to-voltage circuit 29. The capacitance of capacitive sensor13 increases as humidity increases, thereby resulting in an increasedvoltage at conductor 43. The capacitance of capacitive sensor 13 is at amaximum when liquid moisture condenses onto capacitive sensor 13. Thiscondensation of liquid moisture onto capacitive sensor 13, occurs whenthe temperature of capacitive sensor 13 is at or below the dew point ofthe ambient air.

With reference to FIG. 5, the output signal of thecapacitance-to-voltage circuit is connected by conductors 45 and 46 tocomparator circuit 47. This output signal is compared to a set pointvoltage previously established in comparator circuit 47. If the signalis less than a pre-established set point, the signal is interpreted asmeaning that fogging of the surface is not present or imminent. If thesignal is equal to or greater to the pre-established set point, thesignal is interpreted as meaning that fogging of the surface is present,imminent or likely to occur, in which case the system activatescondensation suppression action.

If the signal from the capacitance-to-voltage circuit is equal to orgreater than the pre-established set point, an electrical signal isdirected to switching circuit 50 through conductors 48 and 49, therebycausing the internal electronic or mechanical contactors of switchingcircuit 50 to close. Thereafter, electrical power is directed fromswitching circuit 50 through conductor 51, which branches intoconductors 53 and 54. Conductor 53 is connected to a single-speed ormultiple-speed fan 55 located within duct 58. When fan 55 is energized,it rotates or increases its speed in order to generate or increase thevolume of airflow directed toward the windscreen, goggles, computermonitor screen, window, electronic equipment enclosure, or othersurface. The TEC, the thermal sensor mechanically bonded thereto, andthe capacitive sensor are positioned within duct 58 upstream of fan 55.

FIG. 5 illustrates a first option (Option 1), according to whichelectrical power is applied by conductor 54 to electrical heating coil57. Both fan 55 and heating coil 57 are electrically grounded by grounds56 and 59 respectively. Energization of heating coil 57 raises thetemperature of the air flowing over the heating coil element andthereafter flowing to and onto the face of the surface, thereby raisingthe temperature of the surface and the ambient space surrounding it soas to preclude condensation, or alternately if condensation is present,vaporizing water droplets deposited thereon.

According to a second option (Option 2), electrical power is applied byconductor 54 to an electric motor or solenoid actuator 60, which iselectrically grounded by ground 61. Electric motor or solenoid actuator60 is connected by linkage arm 63 to damper 62, which moves as indicatedin FIG. 5 so as to divert the airstream to an adjacent butinterconnecting and parallel duct 65 within which a heater core 64 ismounted. Heater core 64 raises the temperature of the airstream passingthrough parallel duct 65. Thereafter, the heated air is directed towardand onto the face of the surface, thereby raising the temperature of thesurface and the ambient space surrounding it so as to precludecondensation, or alternately if condensation is present, vaporizingwater droplets deposited thereon.

As a further option, the hot side face of the TEC may be used to provideheat, in lieu of the heating coil 57 or heater core 64, to the airflowing toward and onto the face of the surface, thereby precludingcondensation, or alternatively if condensation is present, vaporizingwater droplets deposited thereon.

As yet a further option, since there will not be any ductwork per se ina helmet or goggles, or within certain other equipment having surfacesto be defogged, fan 55, heating coil 57 and heater core 64 may bereplaced by a heating coil embedded in or on the visor, etc., asmicro-fine electro-resistive wires, or by an infrared source positionedso as to radiate onto the surface.

With reference to FIG. 7, once the automatic sensing and condensationprevention and removal system is powered up, the difference intemperature between the windscreen, goggles, helmet visor, computermonitor screen, window, electronic equipment enclosure, or other surfaceand the TEC is monitored to determine whether it is lower than apre-established set point, and the TEC is energized to the extentnecessary-to raise the difference to the set point. Also, the capacitivesensor is monitored to determine whether it indicates the presence ofcondensation. If the capacitive sensor indicates the presence ofcondensation a fan is energized, and either a heating coil or a damperactuator is activated.

With reference to FIG. 8, an alternative embodiment of an automaticsensing and condensation preclusion and removal system according to theinvention includes two thermal sensors 68 and 71. Thermal sensor 68 ismechanically affixed to or embedded within surface 66, for whichcondensation conditions are to be monitored and/or from which condensateliquid is to be removed. Surface 66 can be, for example, a windscreenfor a vehicle, a visor for a military helmet, pilot helmet, space-suithelmet, or other type of helmet, a visor for safety or non-safetyapparatus, goggles, glasses, or other type of visor or goggle, afull-face air purifying respirator mask, a self-contained breathingapparatus (SCBA) mask, or other type of respirator mask, a computermonitor screen (such as a screen for a commercial electron beam or LCDcomputer monitor placed outdoors, in a cool or cold environment or in ahigh-humidity environment, such as in an industrial panel), a window orother transparent or translucent pane or enclosure (such as commonwindows in office buildings or enclosures that may house documents orother sensitive materials such as artwork and artifacts in museums orhistoric works), including plastics, an electronic equipment enclosure(such as a transparent or non-transparent enclosure for computerequipment, telecommunication equipment, cameras, projection equipment,transmitters, receivers, transceivers, or like components or objectsthat may be placed outdoors or in cool or cold environments or inhigh-humidity environments in which condensation might appear), opticalequipment such as telescopes, binoculars, instrument bezels, viewingwindows, eyeglasses and prescription lenses, electronic circuitry andcircuit boards, and like components.

As schematically shown, the sensors may each be a thermocouple, formedby the fusion of two dissimilar metal conductors, a resistancetemperature detector (RTD), a thermistor, or any electronic thermalmeasurement device performing the same function. Thermal sensor 68 iselectrically connected to conductors 69 and 70, while thermal sensor 71,positioned adjacent to and in close proximity to surface 66, at distance72, in the ambient surroundings 67, is electrically connected toconductors 73 and 74. Additionally, a humidity sensor 75, illustrated asa thin-film capacitive relative humidity sensor, but which may be anyother sensing device that performs a similar function is positionedimmediately adjacent to thermal sensor 71, but also may be mechanicallyaffixed to or otherwise mechanically attached to thermal sensor 71, italso being in close proximity to surface 66, at distance 72, in theambient surroundings 67. Capacitive sensor 75 is electrically connectedto conductors 76 and 77.

With reference to FIG. 9, thermal sensor 68 may be mechanically affixedto surface 66 by means of adhesive 78 (Option 1), or thermal sensor 68may be imbedded within surface 66 (Option 2).

With reference to FIG. 10, in one embodiment of the circuitry for acondensation detection and suppression system of the type shown in FIG.8, thermal sensor 79, illustrated as a negative temperature coefficient(NTC) thermistor, but which may be any other temperature-sensing devicethat performs a similar function, is positioned within ambient space 81.Thin-film relative humidity sensor 80 is also positioned within theambient space 81, in close proximity to thermal sensor 79. A secondthermal sensor 82 is embedded within or affixed to surface 83. The firstthermal sensor 79 is part of a voltage divider circuit, formed by a DCvoltage source, resistor 86, conductors 84 and 85, and ground 87.Similarly, the second thermal sensor 82 is part of a second voltagedivider circuit, formed by a DC voltage source of the same potential,resistor 90, conductors 88 and 89, and ground 91. As is illustrated inthis embodiment, the resistance of each thermal sensor is proportionalto the temperature of the material surrounding it. Thus, in the ambientspace, the resistance of thermal sensor 79, and hence the voltage acrossthermal sensor 79, is proportional to the temperature of the air in theambient space, resulting in a finite voltage input through conductor 84to the analog-to-digital converter (ADC) 92 relative to ground 93. ADC92 is supplied power through conductor 104 by voltage regulator circuit103 that is connected to a DC power source.

Similarly, the resistance of thermal sensor 82, and hence the voltageacross thermal sensor 82, is proportional to the temperature of surface83, resulting in a finite voltage input to ADC 96 through conductor 94relative to ground 95. ADC 96 is supplied power through conductor 106 bya voltage regulator circuit 105 that is connected to a DC power source.

Ambient air or outside air flows over thin-film capacitive sensor 80 inthe ambient space 81. The capacitance of capacitive sensor 80 isproportional to the relative humidity of the surrounding air. Thin filmcapacitive sensor 80 is connected by conductors 97 and 98 to thecapacitance-to-voltage circuit 99, the relative humidity level thusresulting in a finite voltage input to ADC 101 through conductor 100relative to ground 102. The capacitance-to-voltage circuit 99 issupplied power through conductor 108 by a voltage regulator circuit 107that is connected to a DC power source. ADC 101 is supplied powerthrough conductor 110 by a voltage regulator circuit 109 that isconnected to a DC power source.

Alternatively, a single voltage regulator connected to conductors 104,106, and 110 and a single DC power source be may used instead ofindividual voltage regulators 103, 105 and 109.

The voltage level across ambient space thermal sensor 79 is converted inADC 92 to a digital signal, thereafter being appropriately modified toaccount for any sensor error or non-linearity, as necessary, bycalibration data 111. Similarly, the voltage level across surfacethermal sensor 82 is converted in ADC 96 to a digital signal, thereafterbeing appropriately modified to account for any sensor error ornon-linearity, as necessary, by calibration data 112. The voltage levelacross the output conductor 100 relative to ground 102 of the ambientspace relative humidity sensor circuit 99 is converted in ADC 101 to adigital signal, thereafter being appropriately modified to account forany sensor error or nonlinearity, as necessary, by calibration data 113.

Internal timer 114 sets the period of data sampling (or data polling)for sample-and-hold buffers 115, 116, and 117, such that the acquisitionof temperature and relative humidity data occurs concurrently. Eachbuffer may be configured to retain such data in flash memory or in astack arrangement, such that the newest data replaces the datapreviously recorded. Subsequently, digital measurement data of ambientspace temperature, surface temperature, and ambient space relativehumidity are input to central processing unit (CPU) 118 for analysis.CPU 118, which retains a pre-programmed digital instruction set,accesses a set-point database 119 during computation to establishwhether condensation preclusion or removal action is indicated. In suchan event, CPU 118 initiates a signal-to-switching circuit 120, therebycausing internal electronic or mechanical contactors to close.Thereafter, DC electrical power relative to ground 122 is directed fromswitching circuit 120 through conductor 121 thus energizing componentsdownstream.

With reference to FIG. 11, conductor 121 at the output of switchingcircuit 120 branches into two conductors 123 and 124. Conductor 123 isconnected to a single-speed or multi-speed fan 125 located within duct129. When fan 125 is energized, it rotates or increases its speed inorder to generate or increase the volume of airflow directed toward thesurface, thereby raising the temperature of the surface and the ambientspace surrounding it so as to preclude condensation, or alternately ifcondensation is present, vaporizing water droplets deposited thereon.

FIG. 11 illustrates a further option (Option 3), according to whichelectrical power is applied by conductor 124 to electric heating coil127. Both the fan and the heating coil are electrically grounded bygrounds 126 and 128 respectively. Energization of heating coil 127raises the temperature of the air flowing over the heating coil elementand thereafter flowing to and onto the face of the surface, therebyraising its temperature and the ambient space surrounding it andprecluding condensation, or alternatively if condensation is present,vaporizing water droplets deposited thereon.

According to a further option (Option 4), electrical power is suppliedby conductor 124 to an electric motor or solenoid actuator 130, which iselectrically grounded by ground 131. Electric motor or solenoid actuator130 is connected by linkage arm 133 to damper 132, which moves asindicated in FIG. 11 so as to divert the airstream to an adjacent butinterconnecting and parallel duct 135 within which a heater core 134 ismounted. Heater core 134 raises the temperature of the airstream passingthrough parallel duct 135. Thereafter, heated air is directed toward andonto the face of the surface, thereby raising the temperature of thesurface and the ambient space surrounding it so as to precludecondensation, or alternately if condensation is present, vaporizingwater droplets deposited thereon.

According to a further option (Option 5), electrical power is suppliedby conductor 124 to TEC controller circuit 136, which is electricallygrounded by ground 128. TEC controller circuit 136 subsequentlyenergizes TEC 138, through electrical conductors 139 and 140. TEC 138 ispositioned relative to duct 129 such that its cold side face directlycontacts the exterior surface of, and is mechanically attached, bonded,or otherwise affixed to duct 129. In the same location, heat sink 141 ismechanically attached, bonded or otherwise affixed to the inside surfaceof duct 129. Heat sink 141 is comprised of a thermally conductivematerial, which may be constructed with fins, protrusions, or similarextensions, as illustrated. Duct 129 extends past TEC 138 and heat sink141, thereafter attaching to a 180-degree elbow 144 of the samecross-sectional area and dimensions as duct 129, and positioned withinthe same plane. Thereafter, elbow 144 attaches to a further duct 143, ofthe same cross-sectional area and dimensions as duct 129, and ispositioned within the same plane as the distal end of elbow 144. Duct143 extends parallel to duct 129 such that it extends past TEC 138 asillustrated. The hot side of TEC 138 directly contacts the exteriorsurface of, and is mechanically attached to, bonded to, or otherwiseaffixed to duct 143. In the same location, heat sink 142 is mechanicallyattached to, bonded to, or otherwise affixed to the inside surface ofduct 143. Heat sink 142 is comprised of a thermally conductive material,which may be constructed with fins, protrusions, or similar extensions,as is illustrated.

In addition to energizing TEC controller 136, switching circuit 120 alsoconcurrently energizes a single-speed or multi-speed fan 125 throughconductor 123. Fan 125 is located within duct 129 and is electricallygrounded by ground 126. When fan 125 is energized, it rotates orincreases its speed in order to generate or increase the volume ofairflow directed through duct 129, the airstream flowing past andthrough TEC cold side heat sink 141, causing moisture in the airstreamto be condensed into droplets 145 and to be removed and thereafter pastand through TEC hot side heat sink 142, so as to be re-heated anddirected toward the surface, thus directing warmed and dehumidified airtoward the surface so as to provide condensation suppression action.Water droplets 145 pass to the lower interior surface of elbow 144 inwhich an opening and drain trap 146 are affixed. Drain trap 146 isconstructed with a loop seal so that air passing through duct 129 andelbow 144 are precluded from escaping through trap 146 by the coalescedcondensate 147 collected therein. As further moisture droplets 145 arecreated that then pass to elbow 144 and into trap 146, the increasedvolume of condensate 147 within trap 146 causes a hydraulic pressureimbalance, resulting in the ejection of condensate, as is illustrated.

A further illustrative embodiment of a condensation detection andsuppression system is shown in FIG. 12. Goggles 148 may be intended forunderwater use such as by swimmers, but may also be of the type used byconstruction workers, carpenters, skiers, hazardous materials workers,the military, pilots, etc. Goggles 148 have a transparent faceplate 149,whose inner surface is to be monitored for defogging purposes, and havea circular hole 150 cut out of upper horizontal seal 151. A sensorcircuit board 152, positioned in an inverted fashion and containing ahumidity sensor and a temperature sensor, is mounted to the underside ofa main circuit board 154. The humidity sensor and temperature sensorreside within a protective enclosure 153, which may be fabricated inpart out of a hydrophobic material, so as to permit the transference ofgases across its boundary but be impermeable to liquid water. Sensorcircuit board 152 and protective shroud 153 extend beneath and protrudebelow the bottom plane of hermetically sealed enclosure 155 such that,when enclosure 155 is affixed to goggles 148 thus mating with upperhorizontal seal 151, circuit board 152 and protective shroud 153 insertwithin hole 150. In such a position, the humidity and temperaturesensors (and protective shroud) are placed within the enclosed ambientspace formed by the goggles' inner surfaces and the wearer's face.

Main circuit board 154 also contains CPU 156, voltage regulators 157,ADC's 158, and integrated switching mechanism 159. Batteries 160 and161, positioned within cylindrical recesses 162 and 163, supplydirect-current electrical power to main circuit board 154 and sensorcircuit board 152. Gasketed threaded end caps 164 and 165 providehermetic sealing of battery enclosures 162 and 163 respectively.

FIG. 13 illustrates the juxtaposition of the device's ambient-spacehumidity and thermal sensor with respect to the hydrophobic protectiveenclosure. Shown rotated along a horizontal axis 180-degrees from thatdepicted in FIG. 12, humidity sensor 166 and thermal sensor 167 aremounted on common sensor circuit board 168 (corresponding to circuitboard 152 of FIG. 12). Protective enclosure 169 (corresponding toprotective enclosure 153 of FIG. 12), also shown rotated from itsposition as depicted in FIG. 12, is of a size and volume sufficient tocompletely envelop the circuit board 168 and its components. Hydrophobiccover 169 ensures that, should liquid water flood the ambient space (inthis case, the space between the inner surface of the goggles and thewearer's face), the device will still work once the water is cleared offof the inner surface of the goggles. Liquid water can still remain inthe bottom of the ambient space, but any that splashes or floods the topof the ambient space (where the sensors reside) is prevented by theprotective hydrophobic cover from fouling the sensors.

With reference to FIG. 14, the ambient space temperature, ambient spacerelative humidity, and surface temperature levels held in thesample-and-hold buffers are supplied to the central processing unit foranalysis according to either of two alternatives as shown. In the firstalternative, the CPU computes or determines, through direct calculation(using the Clausius-Clapeyron Equation or any of its derivatives), byaccessing an internal look-up table, or by sequentially accessing alook-up table and interpolating or extrapolating and calculation, thetheoretical saturated steam pressure in the ambient space at the ambientspace temperature. Thereafter, the CPU multiplies this ambient spacesaturated steam pressure value by the ambient space relative humiditylevel supplied to it, so as to determine the actual partial pressure ofsteam in the ambient space. Thereafter, the CPU computes or determines,through direct calculation (using the Clausius-Clapeyron Equation or anyof its derivatives), by accessing an internal look-up table, or bysequentially accessing a look-up table and interpolating orextrapolating and calculation, the theoretical saturated steam pressureat the surface temperature previously provided to the CPU. Finally, theCPU compares, by division, the ambient space steam partial pressure tothe saturated steam pressure at the surface temperature, to obtain a“pseudo RH” value. This computed value is then compared to the valuelimit or limits stored in a set-point database. For example, if thevalue is 1.0 or greater, then condensation either exists on the surfacebeing monitored or is imminent, and defogging action is initiated. Ifthe value is about 0.93 to 1.0, condensation is likely, and preclusivedefogging action is initiated. If the value is less than about 0.93,condensation is not likely, and no action is required. Thus, in theevent that the computed value is within the bounds or constraints of thedatabase, no action is taken to preclude condensation conditions orremove condensation on the surface. The device then nulls input datavalues, returns and re-polls the sample and hold buffers and performs afurther computational analysis as previously described. In the eventthat the computed value is outside the bounds or constraints of thedatabase, action is taken to preclude condensation conditions and/orremove condensation on the surface. While this action continues, thedevice nulls input data values, returns and re-polls the sample and holdbuffers, and performs a further computational analysis as described.Condensation preclusion and/or removal action continues until such timethat the ratio of the computed ambient space steam partial pressure tothe saturated steam at the surface temperature is within the bounds orconstraints of the set-point data base.

In a second alternative, the CPU computes or determines, through directcalculation (using the Clausius-Clapeyron Equation or any of itsderivatives), by accessing an internal look-up table or by sequentiallyaccessing a look-up table and interpolating or extrapolating andcalculation, the theoretical saturated steam pressure in the ambientspace at the ambient space temperature provided to the CPU. Thereafter,the CPU multiplies this ambient space saturated steam pressure value bythe ambient space relative humidity level supplied to it, so as todetermine the actual partial pressure of steam in the ambient space.Thereafter, the CPU computes or determines, through direct calculation(using the Clausius-Clapeyron Equation or any of its derivatives), byaccessing an internal look-up table or by sequentially accessing alook-up table and interpolating or extrapolating and calculation, thedew-point temperature of the ambient space steam partial pressure. Thisvalue is subtracted from the temperature of the surface, to result in a“pseudo dew point difference” value. Finally, if the CPU-computed valueis within the bounds or constraints of the database, no action is takento preclude condensation conditions or remove condensation on thesurface. The device then nulls input data values, returns and re-pollsthe sample and hold buffers, and performs a further computationalanalysis as previously described. In the event that the value is outsidethe bounds or constraints of the database, action is taken to precludecondensation conditions and/or remove condensation on the surface. Forexample, if the value is greater than about seven, condensation is notlikely, and no action is required. If the value is zero or less, thencondensation either exists on the surface being monitored or isimminent, and defogging action is initiated. If the value is betweenzero and about seven, condensation is likely, and preclusive defoggingaction is initiated. While this action continues, the device nulls inputdata values, returns and re-polls the sample-and-hold buffers, andperforms a further computational analysis as described. Condensationpreclusion and/or removal action continues until such time that thedifference between the ambient space dew-point temperature and surfacetemperature is within the bounds or constraints of the set-pointdatabase.

There have been described devices and methods for sensing condensationconditions, and for preventing and removing such condensation fromsurfaces. It will be apparent to those skilled in the art that numerousadditions, subtractions, and modifications of the described devices andmethods are possible without departing from the spirit and scope of theappended claims. For example, instead of the condensation preclusionand/or removal mechanisms being activated directly by the circuitrydisclosed herein, the circuitry could provide a warning to a user of avehicle that includes the windscreen, the goggles, the helmet thatincludes the visor, the computer monitor that includes the screen, theroom or enclosure that includes the window, the electronic equipmentthat includes the enclosure, etc., thereby causing the condensationpreclusion and/or removal mechanism to be activated by the user.

What is claimed is:
 1. A device that determines condensation conditionsand suppresses condensation having a given physical state from asurface, comprising: a first thermal sensor in thermally conductivecontact with the surface; a second thermal sensor in an environmentseparated from the surface; a humidity sensor in the environment of thesecond thermal sensor; a condensation suppression mechanism configuredto suppress condensation having the given physical state from thesurface; and a circuit configured to cause the condensation suppressionmechanism to be activated when a temperature sensed by the first thermalsensor, a temperature sensed by the second thermal sensor, and ahumidity sensed by the humidity sensor indicate that a condensationcondition requires suppression at the surface; wherein the environmentof the second thermal sensor is an ambient space with respect to thesurface, and the second thermal sensor is positioned at a sufficientdistance from the surface in the ambient space such that the ambientspace precludes thermal transfer between the surface and the secondthermal sensor.
 2. The device of claim 1 wherein the circuit determinesthat the condensation condition requires suppression at the surface bydetermining, from the temperature sensed by the second thermal sensorand the humidity sensed by the humidity sensor, the pressure of steam inthe environment of the second thermal sensor.
 3. The device of claim 2wherein the circuit determines that the condensation condition requiressuppression at the surface by determining a ratio of the pressure ofsteam in the environment of the second thermal sensor to the saturatedsteam pressure at the temperature sensed by the first thermal sensor. 4.The device of claim 2 wherein the circuit determines that thecondensation condition requires suppression at the surface bydetermining a difference between a temperature sensed by the firstthermal sensor and a dew point temperature associated with the pressureof steam in the environment of the second thermal sensor.
 5. The deviceof claim 1 wherein the condensation condition is a presence ofcondensation on the surface, and the condensation suppression mechanismis a condensation removal mechanism configured to remove condensationhaving the given physical state from the surface the device.
 6. Thedevice of claim 1 wherein the condensation condition is a near presenceof condensation on the surface, and the condensation suppressionmechanism is a condensation preclusion mechanism configured to precludecondensation having the given physical state from the surface thedevice.
 7. The device of claim 1 wherein the given physical state is aliquid state.
 8. The device of claim 1 wherein the surface is awindscreen.
 9. The device of claim 8 wherein the surface is a windscreenof a vehicle.
 10. The device of claim 1 wherein the surface is a helmetvisor.
 11. The device of claim 1 wherein the surface is a computermonitor screen.
 12. The device of claim 1 wherein the surface is awindow.
 13. The device of claim 1 wherein the surface is an enclosurefor electronic equipment.
 14. The device of claim 1 wherein the surfaceis an eyewear surface.
 15. The device of claim 14 wherein the eyewearsurface comprises goggles.
 16. The device of claim 15 wherein thegoggles are underwater goggles.
 17. The device of claim 1 wherein thesurface is a respirator mask surface.
 18. The device of claim 1 whereinthe surface is an optical equipment surface.
 19. The device of claim 1wherein the surface is an electronic circuitry surface.
 20. The deviceof claim 1 wherein the first and second thermal sensors arethermocouples.
 21. The device of claim 1 wherein at least one of thefirst and second thermal sensors is a negative temperature coefficientthermistor.
 22. The device of claim 1 wherein the first thermal sensoris in actual physical contact with the surface.
 23. The device of claim1 wherein the first thermal sensor is affixed to the surface.
 24. Thedevice of claim 1 wherein the first thermal sensor is embedded withinthe surface.
 25. The device of claim 1 wherein the humidity sensor is acapacitive sensor.
 26. The device of claim 1 wherein the condensationsuppression mechanism comprises a fan.
 27. The device of claim 1 whereinthe condensation suppression mechanism comprises a heating mechanism.28. The device of claim 1 wherein the condensation suppression mechanismcomprises a mechanism configured to divert an airstream through a ducthaving a heating mechanism contained therein.
 29. The device of claim 1wherein the condensation suppression mechanism comprises an infraredsource.
 30. The device of claim 1 wherein the condensation suppressionmechanism comprises a thermoelectric cooler having a cold side thatcauses moisture in an airstream to be condensed into liquid water and ahot side that subsequently re-heats the airstream.
 31. The device ofclaim 1 wherein the circuit configured to cause the condensationsuppression mechanism to be activated is configured to directly activatethe condensation suppression mechanism.
 32. A device that determinescondensation conditions and suppresses condensation having a givenphysical state from a surface, comprising: a first thermal sensor inthermally conductive contact with the surface; a second thermal sensorin an environment separated from the surface, the environment being anambient space with respect to the surface; a humidity sensor in theenvironment of the second thermal sensor; a condensation suppressionmechanism configured to suppress condensation having the given physicalstate from the surface; a circuit configured to cause the condensationsuppression mechanism to be activated when a temperature sensed by thefirst thermal sensor, a temperature sensed by the second thermal sensor,and a humidity sensed by the humidity sensor indicate that acondensation condition requires suppression at the surface; and aprotective enclosure enclosing at least the humidity sensor in closeproximity to the humidity sensor, the protective enclosure protectingthe humidity sensor from exposure to liquid water.
 33. The device ofclaim 32 wherein the protective enclosure further encloses the secondthermal sensor and protects the second thermal sensor from exposure toliquid water.
 34. The device of claim 32 wherein the protectiveenclosure is a hydrophobic cover that protects the humidity sensor fromexposure to liquid water while permitting transference of gas across itsboundary.
 35. A method of determining condensation conditions andsuppressing condensation having a given physical state from a surfacehaving a first thermal sensor in thermally conductive contact therewith,comprising: sensing a temperature using the first thermal sensor;sensing a temperature using a second thermal sensor in an environmentseparated from the surface; sensing humidity using a humidity sensor inthe environment of the second thermal sensor; causing a condensationsuppression mechanism to be activated in order to suppress condensationhaving the given physical state from the surface when the temperaturesensed by the first thermal sensor, the temperature sensed by the secondthermal sensor, and the humidity sensed by the humidity sensor indicatethat a condensation condition requires suppression at the surface;wherein the environment of the second thermal sensor is an ambient spacewith respect to the surface, and the second thermal sensor is positionedat a sufficient distance from the surface in the ambient space such thatthe ambient space precludes thermal transfer between the surface and thesecond thermal sensor.
 36. The method of claim 35 wherein the step ofcausing the condensation suppression mechanism to be activated comprisesdetermining that the condensation condition requires suppression at thesurface by determining, from the temperature sensed by the secondthermal sensor and the humidity sensed by the humidity sensor, thepressure of steam in the environment of the second thermal sensor. 37.The method of claim 36 wherein the step of determining that thecondensation condition requires suppression at the surface comprisesdetermining a ratio of the pressure of steam in the environment of thesecond thermal sensor to the saturated steam pressure at the temperaturesensed by the first thermal sensor.
 38. The method of claim 36 whereinthe step of determining that the condensation condition requiressuppression at the surface comprises determining a difference between atemperature sensed by the first thermal sensor and a dew pointtemperature associated with the pressure of steam in the environment ofthe second thermal sensor.
 39. The method of claim 35 wherein thecondensation condition is a presence of condensation on the surface, andthe condensation suppression mechanism is a condensation removalmechanism configured to remove condensation having the given physicalstate from the surface the device.
 40. The method of claim 35 whereinthe condensation condition is a near presence of condensation on thesurface, and the condensation suppression mechanism is a condensationpreclusion mechanism configured to preclude condensation having thegiven physical state from the surface the device.
 41. The method ofclaim 35 wherein the given physical state is a liquid state.
 42. Themethod of claim 35 wherein the surface is a windscreen.
 43. The methodof claim 35 wherein the surface is an eyewear surface.
 44. The method ofclaims 43 wherein the eyewear surface comprises goggles.
 45. The methodof claim 44 wherein the goggles are underwater goggles.
 46. The methodof claim 44 wherein a protective enclosure encloses at least thehumidity sensor, the protective enclosure protecting the humidity sensorfrom exposure to liquid water.
 47. The method of claim 46 wherein theprotective enclosure further encloses the second thermal sensor andprotects the second thermal sensor from exposure to liquid water. 48.The method of claim 35 wherein the humidity sensor is a capacitivesensor.